Yasukiyo Umemura

Isolation and characterization of uridine diphosphate fructose from tubers of jerusalem artichoke (Helianthus tuberosus L.).

Abstract Uridine diphosphate fructose was isolated in a pure state from the acid-soluble extracts of Jerusalem artichoke tubers. The yield was 1.3 μmoles from 10 kg of peeled tubers. This substance contained 2 moles of phosphate, 1 mole of acid-labile phosphate, and 1 mole of acid-labile fructose per mole of uridine. Hydrolysis of this compound with snake venom nucleotide pyrophosphatase gave rise to fructose phosphate and uridine monophosphate; thus, a structure is indicated in which uridine monophosphate is linked to fructose phosphate through the pyrophosphate linkage. The rate of hydrolysis of this compound in 0.01 n hydrochloric acid at 100 ° was determined.

In vitro autodegradation of ribosomal RNA formation of specific fragments with endonucleolytic cleavages

Summary When incubated in vitro with EDTA, ribosomal RNA in fetal rat liver polysomes was degraded to produce fragments some of which have molecular weights similar to those of in vivo degradation intermediates of 28S ribosomal RNA. The degradation occurred endonucleolytically and was inhibited by SDS and liver “cell sap”.

Minor components of rat liver ribosomal RNA as possible intermediates in the degradation of 28S RNA in vivo effects of partial hepatectomy and starvation on their relative amounts.

The minor RNA components in large ribosomal subunits of rat liver were analyzed by gel electrophoresis. Quantitative analysis showed that these minor components, whose apparent molecular weights ranged from 8.48×105 to 11.4×105, represented 10 to 13% of the total high-molecular-weight ribosomal RNA. It was elucidated that they were not artifacts arose during the cell homogenization, subcellular fractionation, RNA preparation and gel electrophoresis. Labeling experiment in vivo showed that they were preferentially present in “old” ribosomes. It was predicted that these minor components were the intermediates in the degradation of 28S ribosomal RNA in vivo. In the regenerating liver, where the degradation of proteins was reported to be blocked, the relative amount of the minor RNA components was decreased to about a half of that of normal liver. There was, however, no increase in their relative amount in the long-term starved rat liver, where RNA degradation should be going very rapidly.